The overall objective of this work is to document the regulation of glycolysis in brain. The research encompasses two aspects of the problem: a detailed study of the factor(s) (probably phospholipid in nature) required for the binding of hexokinase to the mitochondrial membrane and a study of the partitioning of hexokinase (HXK), phospho-glucose isomerase (PGI), phosphofructokinase (PFK) and creatine kinase (CK) between mitochondria and cytosol as a function of the energy status of nerve cells. Goals set for the next year are conversion of purified brain hexokinase which has lost its ability to bind to brain hexokinase back into the bindable form and documentation of the components of the outer mitochondrial membrane required for binding hexokinase. Our studies on the metabolic conditions which influence the binding of hexokinase to the mitochondrial membrane in isolated neuronal perikarya are nearly complete; we plan to extend this experimental approach to the study of the subcellular distribution of other glycolytic enzymes and creatine kinase.